A magnetic compass points approximately to the north magnetic pole
(and away from the south magnetic pole). Approximately, because in addition
to the core field there are fields generated in the crust and mantle which
vary by location. The difference between true north and magnetic north at
any location is known as the magnetic variance or declination and can be
measured, or calculated using one of several different models. The variance
is important to know for accurate navigation using a magnetic compass.

The Great Circle Mapper now includes the variation on each airport page, and
for each path shows the initial magnetic heading in addition to the initial
(true) heading. These values are calculated using the
World Magnetic Model (WMM).

Information on this site may not be accurate or current and is not valid for flight planning or navigation. No warranty of fitness for any purpose is made or implied. Flight planning and navigation should only be done using official charts.